Various types of pumps such as booster pumps and deep well pumps, for example, normally tend to introduce starting and stopping liquid surges. Start up of such a pump may introduce a suddenly increased pressure into the main line system creating an undesirable surge. Particularly in a deep well pump at least sections of the line at the discharge side of the pump may be partly filled with air and, upon startup of the pump, it is common to discharge the initial mixture of air and liquid to the atmosphere. When such venting is completed, and a venting valve closed, the rapidly flowing liquid may suddenly impinge upon liquid in the mainline system, creating a significant and undesirable shock and surge. A similar shock and surge will occur upon startup of a booster pump.
When such pumps are shut down, momentum of flowing liquid may create a decreased pressure or suction effect in the vicinity of the pump discharge. System liquid, no longer subject to the pump pressure, will continue to flow for a short time, then will return toward the pump, and will surge back and forth.
To avoid such surging, pumps are often connected to operate together with an anti-surge valve or a pump control valve, which, in effect, isolates the mainline hydraulic system from the pump during pump start and stop periods. For example, in a booster pump, a valve is provided to receive discharge of the pump and is maintained in a closed condition, isolating the mainline system from the pump discharge, when the pump is started. Upon start of the pump, the valve begins to open, and opens slowly, to allow pump discharge pressure to be relatively slowly and gradually transmitted to the mainline hydraulic system. Conversely, the valve is caused to begin to close, and closes slowly, before the pump is stopped. Thus, the pump pressure is gradually removed from the system and surge is avoided.
For deep well pumps, the operation is similar but the anti-surge valve is the vent valve and is open when the pump is started to connect the pump discharge to the atmosphere. When the pump is started, this anti-surge vent valve begins to close and, as it begins to close, the main valve connecting the pump discharge to the mainline hydraulic system begins to open. In the deep well pump, a stop command to the pump does not stop the pump but rather begins the opening of the vent valve and the pump is stopped only after such valve has opened to a significant degree.
Such an anti-surge valve and pump system for a booster pump is described in U.S. Pat. No. 2,384,420 to D. G. Griswold, assigned to Clayton Manufacturing Co., the predecessor of the assignee of the present invention. Such assignee presently manufactures such pump control valves. A typical booster type pump control valve is identified as Clayton Model No. 60P-1A (Globe) and a typical deep well type pump control valve as identified as Clayton Model No. 61P-2A (Globe), both manufactured by Cla-Val Co. of Newport Beach Calif., the assignee of the present invention.
It is found that buyers of these valves may not always connect the valve for proper electrical operation. Further, certain types of system failures have occurred with the use of this type of pump control or anti-surge valve. Thus, because of damage to the equipment, improper connection, or certain types of system failures, it is possible that the pump will start and continue to run even though, for example, the booster type pump control valve fails to open. This may result in severe damage to the pump and motor.
Other problems can occur. The pump may continue to run or the valve may continue to be in its operating condition even if there is a mechanical or hydraulic failure. A temporary power failure may allow an automatic restart upon resumption of power even though the valve (in a booster pump, for example) is still open and has not yet closed. Where the pump loses suction or discharge pressure decreases below a selected value, the pump may continue to run and the valve (such as the booster valve, for example) may remain open. In certain deep well pump operations, the initially open vent valve may close before the fully liquid (without intermixed air) discharge of the deep well pump reaches this valve.
Any of these possibilities can result in severe damage to the system or its components. Nevertheless, there has been devised no safety control system to adequately handle such potentially damaging conditions.
Accordingly, it is an object of the present invention to control a pump control valve and pump so as to avoid or eliminate the above-mentioned problems.